With the improvement in the design and the manufacturing techniques of the smart mobile phone, smart mobile phones with high display proportion has quickly become dominant in the market and a vital developing direction in recent years. The camera of the smart mobile phone has not been capable of penetrating through a display for photographing yet, that is, the camera should be designed at a region out of the display screen, moreover, the improvement of the display screen proportion means further decrease in the space on the periphery of the mobile phone for installing the camera, therefore, for a mobile phone with high display proportion, the camera should be hidden at a back side of the display screen, and the camera retracts when not to be used and extends out of the display screen for photographing when to be used.
In the prior art, the screw-and-nut transmission type is commonly adopted to drive the extending and retracting movement of the camera, however, because of the small dimensions and therefore the relatively weak strength of the components, the screw tends to be stuck, which would affect the transmission efficiency, or tends to be loosen, which would result in failure.